Production · 2026-07-14
The Quality Window: Why Harvest Timing Decides Salt Purity
Between gypsum saturation and bittern breakthrough sits a narrow density band. Managing it is the difference between 97% and 99.4% NaCl.
Solar salt is a controlled crystallisation process, not simply an act of evaporation. Seawater entering the concentrator ponds at roughly 3.5 degrees Baumé is walked through a cascade in which calcium carbonate and calcium sulphate drop out first. Sodium chloride only becomes the dominant precipitate above 25.7 degrees Baumé, and it remains clean until magnesium and potassium salts begin to co-crystallise near 29 degrees.
That leaves a working window of roughly three degrees. Harvest too early and yield collapses; harvest too late and the crystal bed traps bittern, lifting magnesium and sulphate above the tolerance of a membrane-cell chlor-alkali buyer. Our crystallisers are therefore density-mapped daily during the harvest season, and each pond is released only when the brine profile and crystal-bed depth agree.
Post-harvest handling matters as much as pond chemistry. Draining the harvested pile on a graded, compacted floor for ten to fourteen days allows residual mother liquor to run off before washing. In practice this single step recovers between three and six tenths of a percent of NaCl purity at almost no processing cost.